Add extra scroll to the candlesticks

android/src/main/java/com/github/fujianlian/klinechart/BaseKLineChartView.java

@@ -1428,11 +1428,25 @@ public int getMinScrollX() {
         return 0;
     }
 
+    public int getExtraScrollX() {
+        return (int) (mOverScrollRange / mScaleX);
+    }
+
     public int getMaxScrollX() {
-        int contentWidth = (int) Math.max((mDataLen - (mWidth - configManager.paddingRight) / mScaleX), 0);
+        int contentWidth = (int) Math.max((mDataLen - (mWidth - configManager.paddingRight) / mScaleX + getExtraScrollX()), 0);
         return contentWidth;
     }
 
+    @Override
+    protected float getMinVisibleCandles() {
+        return configManager.minVisibleCandles;
+    }
+
+    @Override
+    public float getDataLength() {
+        return mDataLen;
+    }
+
     /**
      * 在主区域画线
      *
@@ -1989,19 +2003,20 @@ public boolean onSingleTapUp(MotionEvent e) {
     }
 
     public void smoothScrollToEnd() {
-        int endScrollX = getMaxScrollX();
-        int currentScrollX = getScrollOffset();
-        int distance = endScrollX - currentScrollX;
-
-        // android.util.Log.d("BaseKLineChartView", "smoothScrollToEnd DEBUG:");
-        // android.util.Log.d("BaseKLineChartView", "  mDataLen=" + mDataLen + ", mItemCount=" + mItemCount + ", mPointWidth=" + mPointWidth);
-        // android.util.Log.d("BaseKLineChartView", "  mWidth=" + mWidth + ", mScaleX=" + mScaleX + ", paddingRight=" + configManager.paddingRight);
-        // android.util.Log.d("BaseKLineChartView", "  current=" + currentScrollX + ", end=" + endScrollX + ", distance=" + distance);
-
-        // Always scroll to end position, regardless of current position
-        // This ensures we go to the rightmost position to show the latest data
-        setScrollX(endScrollX);
-        // android.util.Log.d("BaseKLineChartView", "Set scroll position to end: " + endScrollX);
+        int screenWidthInLogicalUnits = getExtraScrollX();
+        int endScrollX = (int)(mDataLen + configManager.paddingRight - screenWidthInLogicalUnits);
+
+        setScrollXWithoutMinCandlesLimit(Math.max(0, endScrollX));
+    }
+
+    /**
+     * Set scroll position without applying minVisibleCandles limit
+     */
+    private void setScrollXWithoutMinCandlesLimit(int scrollX) {
+        int oldX = this.mScrollX;
+        this.mScrollX = Math.max(0, Math.min(scrollX, (int)mDataLen));
+        onScrollChanged(this.mScrollX, 0, oldX, 0);
+        invalidate();
     }
 
     // Public getter methods for accessing protected fields

android/src/main/java/com/github/fujianlian/klinechart/HTKLineConfigManager.java

@@ -103,6 +103,8 @@ public class HTKLineConfigManager {
 
     public float candleCornerRadius = 0;
 
+    public float minVisibleCandles = 5;
+
     public int minuteVolumeCandleColor = Color.RED;
 
     public float minuteVolumeCandleWidth = 1.5f;
@@ -455,6 +457,11 @@ public void reloadOptionList(Map optionList) {
             this.candleCornerRadius = candleCornerRadiusValue.floatValue();
         }
 
+        Number minVisibleCandlesValue = (Number)configList.get("minVisibleCandles");
+        if (minVisibleCandlesValue != null) {
+            this.minVisibleCandles = minVisibleCandlesValue.floatValue();
+        }
+
         this.fontFamily = (configList.get("fontFamily")).toString();
         this.textColor = ((Number) configList.get("textColor")).intValue();
         this.headerTextFontSize = ((Number)configList.get("headerTextFontSize")).floatValue();

android/src/main/java/com/github/fujianlian/klinechart/ScrollAndScaleView.java

@@ -17,6 +17,12 @@ public abstract class ScrollAndScaleView extends RelativeLayout implements
         GestureDetector.OnGestureListener,
         ScaleGestureDetector.OnScaleGestureListener {
     protected int mScrollX = 0;
+
+    /**
+     * Get minimum visible candles
+     * @return minimum number of candles that should be visible
+     */
+    protected abstract float getMinVisibleCandles();
     protected GestureDetectorCompat mDetector;
     protected ScaleGestureDetector mScaleDetector;
 
@@ -265,6 +271,20 @@ public boolean isTouch() {
      */
     public abstract int getMaxScrollX();
 
+    /**
+     * Get the point width
+     *
+     * @return
+     */
+    public abstract float getPointWidth();
+
+    /**
+     * Get the total data length (itemCount * pointWidth)
+     *
+     * @return
+     */
+    public abstract float getDataLength();
+
     /**
      * Set ScrollX
      *
@@ -286,7 +306,6 @@ public boolean isMultipleTouch() {
 
     protected void checkAndFixScrollX() {
         int contentSizeWidth = (getMaxScrollX());
-
         if (mScrollX < getMinScrollX()) {
             mScrollX = getMinScrollX();
             mScroller.forceFinished(true);

android/src/main/java/com/github/fujianlian/klinechart/container/HTKLineContainerView.java

@@ -79,16 +79,16 @@ public void reloadConfigManager() {
         klineView.setMTextSize(klineView.configManager.candleTextFontSize);
         klineView.setMTextColor(klineView.configManager.candleTextColor);
         klineView.reloadColor();
-        Boolean isEnd = klineView.getScrollOffset() >= klineView.getMaxScrollX();
         int previousScrollX = klineView.getScrollOffset();
         klineView.notifyChanged();
 
         if (klineView.configManager.shouldAdjustScrollPosition) {
             // 调整滚动位置以补偿新增的数据
             int newScrollX = previousScrollX + klineView.configManager.scrollPositionAdjustment;
             klineView.setScrollX(newScrollX);
-        } else if (isEnd || klineView.configManager.shouldScrollToEnd) {
-            klineView.setScrollX(klineView.getMaxScrollX());
+        } else if (klineView.configManager.shouldScrollToEnd) {
+            int scrollToEnd = klineView.getMaxScrollX() - klineView.getExtraScrollX();
+            klineView.setScrollX(scrollToEnd);
         }
 
 
@@ -410,7 +410,7 @@ public void addCandlesticksAtTheEnd(ReadableArray candlesticksArray) {
 
         try {
             // Check if user is currently at the end of the chart
-            boolean wasAtEnd = klineView.getScrollOffset() >= klineView.getMaxScrollX() - 10;
+            boolean wasAtEnd = klineView.getScrollOffset() >= klineView.getMaxScrollX() - 10 - klineView.getExtraScrollX();
 
             // Get existing model for preserving indicator lists structure
             KLineEntity templateEntity = null;

example/App.js

@@ -42,6 +42,7 @@ import {
 
 
 const App = () => {
+	const MIN_VISIBLE_CANDLES = 10
 	const [isDarkTheme, setIsDarkTheme] = useState(false)
 	const [selectedTimeType, setSelectedTimeType] = useState(2) // Corresponds to 1 minute
 	const [selectedMainIndicator, setSelectedMainIndicator] = useState(1) // Corresponds to MA (1=MA, 2=BOLL)
@@ -167,7 +168,8 @@ const App = () => {
 			lastDataLength,
 			currentScrollPosition,
 			showVolumeChart,
-			candleCornerRadius
+			candleCornerRadius,
+			minVisibleCandles: MIN_VISIBLE_CANDLES
 		}, shouldScrollToEnd, kLineViewRef.current ? true : false)
 		setOptionListValue(newOptionList)
 	}, [klineData, selectedMainIndicator, selectedSubIndicator, showVolumeChart, isDarkTheme, selectedTimeType, selectedDrawTool, showIndicatorSelector, showTimeSelector, showDrawToolSelector, drawShouldContinue, optionList, lastDataLength, currentScrollPosition, candleCornerRadius])
@@ -216,7 +218,8 @@ const App = () => {
 			lastDataLength,
 			currentScrollPosition,
 			showVolumeChart,
-			candleCornerRadius
+			candleCornerRadius,
+			minVisibleCandles: MIN_VISIBLE_CANDLES
 		}, false)
 
 		// Calculate scroll distance adjustment needed (based on item width)

example/utils/businessLogic.js

@@ -282,7 +282,8 @@ export const packOptionList = (modelArray, appState, shouldScrollToEnd = true, u
 		selectedDrawTool,
 		showVolumeChart,
 		candleCornerRadius,
-		drawShouldContinue
+		drawShouldContinue,
+		minVisibleCandles
 	} = appState
 
 	const theme = ThemeManager.getCurrentTheme(isDarkTheme)
@@ -355,6 +356,7 @@ export const packOptionList = (modelArray, appState, shouldScrollToEnd = true, u
 		itemWidth: 8 * pixelRatio,
 		candleWidth: 6 * pixelRatio,
 		candleCornerRadius: candleCornerRadius * pixelRatio,
+		minVisibleCandles: minVisibleCandles || 5,
 		minuteVolumeCandleColor: processColor(showVolumeChart ? COLOR(0.0941176, 0.509804, 0.831373, 0.501961) : 'transparent'),
 		minuteVolumeCandleWidth: showVolumeChart ? 2 * pixelRatio : 0,
 		macdCandleWidth: 1 * pixelRatio,

ios/Classes/HTKLineConfigManager.swift

@@ -134,6 +134,8 @@ class HTKLineConfigManager: NSObject {
 
     var candleCornerRadius: CGFloat = 0
 
+    var minVisibleCandles: CGFloat = 5
+
     var minuteVolumeCandleWidth: CGFloat = 0
 
     var _minuteVolumeCandleWidth: CGFloat = 0
@@ -448,6 +450,7 @@ class HTKLineConfigManager: NSObject {
         _minuteVolumeCandleWidth = configList["minuteVolumeCandleWidth"] as? CGFloat ?? 0
         _macdCandleWidth = configList["macdCandleWidth"] as? CGFloat ?? 0
         candleCornerRadius = configList["candleCornerRadius"] as? CGFloat ?? 0
+        minVisibleCandles = configList["minVisibleCandles"] as? CGFloat ?? 5
         reloadScrollViewScale(1)
         paddingTop = configList["paddingTop"] as? CGFloat ?? 0
         paddingRight = configList["paddingRight"] as? CGFloat ?? 0

ios/Classes/HTKLineView.swift

@@ -131,16 +131,25 @@ class HTKLineView: UIScrollView {
             childDraw = wrDraw
         }
 
-        let isEnd = contentOffset.x + 1 + bounds.size.width >= contentSize.width
         let previousContentOffset = contentOffset.x
         reloadContentSize()
 
+
+        let rightScreenOffset = contentOffset.x + bounds.size.width + 1
+        let lastCandlestickOffset = contentSize.width - bounds.size.width - configManager.itemWidth / 2
+        // how many candlesticks +- should it consider to auto scroll to end when new data is added
+        // if the user is over-scrolled, then the candlesticks have space to appear on screen without scrolling
+        // and at some point it will enter this range and become auto-scrolling to end
+        let candlesticksCountOffset = 1.5 * configManager.itemWidth
+        // Extra spacing at the end is bounds.size.width
+        let isEnd = lastCandlestickOffset - candlesticksCountOffset <= rightScreenOffset && rightScreenOffset <= lastCandlestickOffset + candlesticksCountOffset
+
         if configManager.shouldAdjustScrollPosition {
             // Adjust scroll position to compensate for newly added data
             let newContentOffset = previousContentOffset + configManager.scrollPositionAdjustment
             reloadContentOffset(newContentOffset, false)
         } else if configManager.shouldScrollToEnd || isEnd {
-            let toEndContentOffset = contentSize.width - bounds.size.width
+            let toEndContentOffset = contentSize.width - 2 * bounds.size.width
             let distance = abs(contentOffset.x - toEndContentOffset)
             let animated = distance <= configManager.itemWidth
             reloadContentOffset(toEndContentOffset, animated)
@@ -183,16 +192,19 @@ class HTKLineView: UIScrollView {
         let contentWidth =
             configManager.itemWidth * CGFloat(configManager.modelArray.count)
             + configManager.paddingRight
+            + bounds.size.width
         contentSize = CGSize.init(width: contentWidth, height: frame.size.height)
     }
 
     func reloadContentOffset(_ contentOffsetX: CGFloat, _ animated: Bool = false) {
-        let offsetX = max(0, min(contentOffsetX, contentSize.width - bounds.size.width))
+        let allCandlesWidth = configManager.itemWidth * CGFloat(configManager.modelArray.count)
+        let maxAllowedOffset = max(0, allCandlesWidth - configManager.minVisibleCandles * configManager.itemWidth)
+        let offsetX = max(0, min(contentOffsetX, maxAllowedOffset))
         setContentOffset(CGPoint.init(x: offsetX, y: 0), animated: animated)
     }
 
     func smoothScrollToEnd() {
-        let endOffsetX = contentSize.width - bounds.size.width
+        let endOffsetX = contentSize.width - 2 * bounds.size.width
         reloadContentOffset(endOffsetX, true)
     }
 
@@ -1034,7 +1046,16 @@ class HTKLineView: UIScrollView {
 extension HTKLineView: UIScrollViewDelegate {
 
     func scrollViewDidScroll(_ scrollView: UIScrollView) {
+        let allCandlesWidth = configManager.itemWidth * CGFloat(configManager.modelArray.count)
+        let maxAllowedOffset = max(0, allCandlesWidth - configManager.minVisibleCandles * configManager.itemWidth)
+
         let contentOffsetX = scrollView.contentOffset.x
+
+        if contentOffsetX > maxAllowedOffset {
+            scrollView.contentOffset.x = maxAllowedOffset
+            return
+        }
+
         var visibleStartIndex = Int(floor(contentOffsetX / configManager.itemWidth))
         var visibleEndIndex = Int(
             ceil((contentOffsetX + scrollView.bounds.size.width) / configManager.itemWidth))